A multipath in radio frequency (RF) communications refers to the existence of multiple paths of RF propagation between a transmitter and a receiver. In situations when the paths contain the same data, but are spaced apart in time, the resultant reception can be destructive. There are however circumstances when it is actually desirable to have multiple paths. In these cases each path can carry a different data stream. This technique is referred to as a layered space approach, or under the broader category of multiple input and multiple output (MIMO) communication systems. If the transmitter and receiver are capable of utilizing each path, the effective data bandwidth of the link between the two can be increased by the number of unique usable paths.
One problem is that not enough natural paths, or existing paths with discernable characteristics, may be exploitable for the capabilities of the transmitters and receivers to be fully utilized. The prior art exploits the elevation variable characteristics of a transmitter. This path may not always be available due to the lack of intervening physical obstacles to scatter the signals. Even when this option is available, it may not provide sufficient paths to fully utilize the ability of the transmitter and receiver.
FIG. 3 illustrates a prior art wireless communication system 300 which includes a transmitter 305 and a receiver 310. The transmitter 305 forms a multipath, (i.e., a first path 315 and an additional path 320), via an elevation antenna pattern. However, the additional path 320 formed by the transmitter 305 is formed by directing a beam towards the ground 325.
Conventional wireless communication systems use beam forming for non-MIMO purpose. Therefore, a method and apparatus is desired for exploiting the RF physical environment by combining beam forming with MIMO to provide a sufficient number of paths.